Hendrik Antoon Lorentz (July 18, 1853, Arnhem – February 4, 1928, Haarlem) was a Dutch physicist who ushered in the era of relativity by developing the ideas behind what became known as the Lorentz-FitzGerald contraction. His theories on the electron earned him a Nobel Prize in Physics that he shared with Pieter Zeeman in 1902.

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Biography

Early life

Hendrik Lorentz was born in Arnhem, Gelderland, son of Gerrit Frederik Lorentz (1822 – 1893), a shopkeeper, and Geertruida van Ginkel (1826 – 1861). When Lorentz was four, his mother died, and his father married Luberta Hupkes. From 1866-1869 Lorentz attended high school in Arnhem, and in 1870 entered the University of Leiden, where he was strongly influenced by the teaching of astronomy professor Frederik Kaiser. It was Kaiser who influenced Lorentz to choose physics as a career. Lorentz was awarded a bachelor's degree in mathematics and physics in 1871, and the following year returned to Arnhem to teach high school night classes in mathematics, while continuing to read for his doctorate. In 1875, Lorentz earned a doctoral degree under Pieter Rijke on a thesis entitled On the theory of reflection and refraction of light, in which he refined the electromagnetic theory of James Clerk Maxwell to account for a wide range of optical phenomena.

In 1881, Hendrik married Aletta Catharina Kaiser, niece of Frederik Kaiser. She was the daughter of Johann Wilhelm Kaiser, director of the Amsterdam's Engraving School and professor of Fine Arts, and designer of the first Dutch postage stamps in 1852. Later Kaiser was the Director of the Rijksmuseum National Gallery of Amsterdam. Lorentz and his wife had three children, of whom the eldest daughter, Geertruida de Haas-Lorentz followed in her father's footsteps and became a physicist.

Professorship in Leiden

In 1878, the 24-year-old Lorentz was appointed to the newly established chair in theoretical physics at the University of Leiden. On January 25, 1878, he delivered his inaugural lecture on "De moleculaire theoriën in de natuurkunde" (The molecular theories in physics).

During his first 20 years in Leiden, Lorentz was primarily interested in investigating the interrelationship of electricity, magnetism, and light. He also wrote on mechanics, thermodynamics, hydrodynamics, kinetic theories, solid state theory, light, and propagation. His most important contributions, however, were in the area of electromagnetism, the theory of the electron, and relativity.

Electrodynamics and "relativity"

In the 1880s, American scientists Albert Michelson and Edward Morley designed and conducted an experiment that failed to detect any motion of the Earth with respect to the ether, the hypothetical medium that was thought to be responsible for the propagation of light. In 1892, in an attempt to explain the Michelson-Morley experiment while retaining the idea of the ether, Lorentz proposed that moving bodies contract in the direction of motion.

George FitzGerald had already arrived at this conclusion using basically the same reasoning. Unlike FitzGerald, however, whose work on the theory was not much more than a brief letter to the journal Science, Lorentz developed the theory and supporting mathematics. He introduced the term local time which varies in reference frames with different uniform velocities relative to one another. Lorentz found that he could not keep the form of Maxwell's equations in different reference frames without assigning each reference frame its own time. Henri Poincaré developed this idea further, and showed how it arose when clocks in moving frames are synchronized by exchanging light signals which are assumed to travel with the same speed against and with the motion of the frame.

In 1899 and again in 1904, Lorentz added time dilation to his transformations and published what Poincaré in 1905 named the Lorentz transformations. It was apparently unknown to Lorentz that Joseph Larmor had predicted time dilation, at least for orbiting electrons, and published the identical transformations in 1897. The equations developed by Larmor and Lorentz are algebraically equivalent to those presented by Henri Poincaré and Albert Einstein in 1905 (Macrossan, 1986). These mathematical formulas contained all the important elements of what later became known as theory of Special relativity, namely the relativistic increase of mass, shortening of length, and time dilation that are characteristic of a moving body, all of which Lorentz had discussed in his 1899 publication.

Albert Einstein and Hendrik Antoon Lorentz, photographed by Ehrenfest in front of his home in Leiden in 1921. Source: Museum Boerhaave, Leiden.

Mass increase was the first prediction of special relativity to be tested, but from early experiments by Kaufmann it appeared that his prediction was wrong; this led Lorentz to the famous remark that he was "at the end of his Latin."[1] Its confirmation had to wait until 1908.

The electron

Related to his attempts to understand the Michelson Morley experiment, Lorentz in 1892 devised a theory of the structure of matter that gave it a strong electromagnetic component. His theory of the atom was that it was composed of two oppositely charged components, one of which was larger than the other and constituted most of the atom's mass.[2] In Lorentz's theory, oscillating charges in the atoms (that he called "ions" but were later named "electrons") were responsible for the interaction between light and matter. This theory gave an explanation for the foreshortening necessitated by the Michelson Morley experiment, in terms of electromagnetic properties.

Pieter Zeeman, a friend, colleague, and former student of Lorentz, became interested in conducting experiments to determine the relationship between light and magnetism in the mid-1890s. Encouraged by the results of Michael Faraday over half a century earlier, Zeeman hoped to determine the effect of a magnetic field on the spectral lines of sodium. His supervisor failed to share his enthusiasm, but Lorentz encouraged Zeeman. Zeeman was able to perform the experiment, burning a sample of a sodium compound between two strong electromagnets and analyzing the resulting spectrum. He detected a change—a splitting of the spectral lines.

Lorentz immediately used the results to make one of the first measurements of the ratio of the charge to the mass of an electron, based on his theory of matter. He could also establish that the electron carried a negative electric charge.[3] A year later, J.J. Thompson used an entirely different but more direct method to measure the same quantity, the results of which closely approximated Lorentz's. Lorentz and Zeeman, mentor and student, were both awarded the Nobel Prize in 1902—Zeeman for his experiments that led to the discovery of the effect that bears his name, and Lorentz for his theory of the electron.

Poincaré (1902) said of Lorentz's theory of electrodynamics:

"The most satisfactory theory is that of Lorentz; it is unquestionably the theory that best explains the known facts, the one that throws into relief the greatest number of known relations … it is due to Lorentz that the results of Fizeau on the optics of moving bodies, the laws of normal and abnormal dispersion and of absorption are connected with each other … Look at the ease with which the new Zeeman phenomenon found its place, and even aided the classification of Faraday's magnetic rotation, which had defied all (James Clerk) Maxwell's efforts." (Poincaré, 1902)

In 1906, Lorentz traveled to America and delivered a series of lectures on relativistic electromagnetic theory. These lectures were published in 1909 under the title Theory of Electrons.[4]

Later years

Lorentz was chairman of the first Solvay Conference held in Brussels in the autumn of 1911. Shortly after the conference, Poincaré wrote an essay on quantum physics, which gives an indication of Lorentz's status at the time:

… at every moment [the twenty physicists from different countries] could be heard talking of the [quantum mechanics] which they contrasted with the old mechanics. Now what was the old mechanics? Was it that of Newton, the one which still reigned uncontested at the close of the nineteenth century? No, it was the mechanics of Lorentz, the one dealing with the principle of relativity; the one which, hardly five years ago, seemed to be the height of boldness. (Poincaré, 1913)

In the same essay, Poincaré lists the enduring aspects of Lorentzian mechanics:

no body in motion will ever be able to exceed the speed of light … the mass of a body is not constant … no experiment will ever be able [to detect] motion either in relation to absolute space or even in relation to the ether. (Poincaré, 1913)

In 1912, Lorentz retired early to become director of research at Teylers Museum in Haarlem, although he remained external professor at Leiden and gave weekly lectures there. Paul Ehrenfest succeeded him in his chair at the University of Leiden, founding the Institute for Theoretical Physics, which would become known as the Lorentz Institute. In addition to the Nobel Prize in Physics, Lorentz received a great many honors for his outstanding work. He was elected a Fellow of the Royal Society in 1905. The Society awarded him its Rumford Medal in 1908 for his investigations of optical and electrical phenomena, and its Copley Medal for his research in mathematical physics in 1918.

While Lorentz is mostly known for fundamental theoretical work, he also had an interest in practical applications. In the years 1918-1926, at the request of the Dutch government, Lorentz headed a committee to calculate some of the effects of the proposed Afsluitdijk (Closure Dike) flood control dam on other seaworks in the Netherlands. Hydraulic engineering was mainly an empirical science at that time, but the disturbance of the tidal flow caused by the Afsluitdijk was so unprecedented that the empirical rules could not be trusted. Lorentz proposed to start from the basic hydrodynamic equations of motion and solve the problem numerically. The Afsluitdijk was completed in 1933 and the predictions of Lorentz and his committee turned out to be remarkably accurate.

In his last years, Lorentz aligned himself with Einstein and his attempt to explain gravity using a line of reasoning that, in a sense, was an extension of Lorentz's. Einstein had given proper credit to Lorentz's ideas, while Lorentz admitted that Poincaré had put the final touches on his own. Lorentz wrote essays for the general public in an attempt to demystify Einstein's general theory of relativity, which had experienced some experimental triumphs in the last decade of Lorentz's life.

Lorentz died in Haarlem, the Netherlands, on February 4, 1928.

The respect that Lorentz held in the Netherlands is seen in O. W. Richardson's description of his funeral [6]:

The funeral took place at Haarlem at noon on Friday, February 10. At the stroke of twelve the State telegraph and telephone services of Holland were suspended for three minutes as a revered tribute to the greatest man Holland has produced in our time. It was attended by many colleagues and distinguished physicists from foreign countries. The President, Sir Ernest Rutherford, represented the Royal Society and made an appreciative oration by the graveside.

Legacy

Lorentz had the foresight to extend Maxwell's work by establishing a theory of matter that led to the discovery of the electron and to the extension of Maxwell's equations to reference frames moving uniformly with respect to one another. Lorentz's work, and that of many of his contemporaries, such as Henri Poincare and Larmor, show that theories of relativity were not confined to those of Einstein, although Einstein took much of the wind out of others' sails by extending his theory to include gravitation.

The importance of the mentor/protege relationship becomes evident in Lorentz's life story. His support for his former student Pieter Zeeman, bore fruit when both shared a Nobel prize in 1902 for their efforts. Lorentz was often consulted during his lifetime on matters relating to the development of twentieth-century physics, although the ideas he shared did not always bear fruit. M. J. Klein (1967) wrote of Lorentz's reputation in the 1920s:

For many years physicists had always been eager "to hear what Lorentz will say about it" when a new theory was advanced, and, even at seventy-two, he did not disappoint them.

It was Lorentz who took the world into a new realm of time and space contraction and variable mass, and led to speculation in popular culture about time travel, potential slowing of the aging process, and other marvelous concepts about time and space.

↑ Albert E. Moyer, 1983. "American physics in transition: a history of conceptual change in the late nineteenth century." The History of Modern Physics, 1800-1950, Vol. 3. (Los Angeles: Tomash Publishers. ISBN 0938228064), 151.

Kox, A.J. March 1996. H.A. Lorentz: Sketches of his work on slow viscous flow and some other areas in fluid mechanics and the background against which it arose. Journal of Engineering Mathematics 30(1-2): ii, 1-18.

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